Yeah, maybe they're getting old. Though, mine was kept unused since i got it, i wanted to extend the range at home but never did it, instead i repositioned the main router and the range i wanted got fixed this way, placing the RT-N66U in the drawer. So from this point of view it's kind of new, that's why i am a little frustrated. I put it into service last summer in July at my remote place where they finally changed my DSL line with fiber optics and it made sense to use a powerful router.It automatically reboots for me and I think it always has. Our routers are getting old so maybe it's a hardware error. Others have suggested changing power adapters for weird hardware issues.
Anyway, great idea with the power brick, i'll try and find something useful and do it.